1. Field of the Invention
The present invention relates generally to improvements in hot exhaust gas pipes and mufflers and more particularly pertains to new and improved decorative exhaust gas pipes and mufflers used on motorcycles and customized automobiles.
2. Description of Related Art
One of the most critical problems confronting the developers of motorcycle exhaust pipes and mufflers or exhaust pipes and mufflers for automobiles which are exposed for appearance purposes has been the prevention of heat discolorization of the chromed exhaust pipes and muffler casings from the extreme heat generated by high engine performance.
Although the prior art has been concerned with preventing heat transfer to the outer housing of a motorcycle exhaust system, none have really accomplished that goal, none have prevented heat discoloration as the present invention. U.S. Pat. No. 4,356,885 for a Chambered-Core Motorcycle-Exhaust Apparatus was granted on Nov. 2, 1982 to Christy J. Dello. The exhaust system described in the Dello patent is concerned with a double wall exhaust system wherein the inner core is mounted within a tubular housing having a larger diameter than the inner core so as to establish an annular chamber between the outer housing and the inner exhaust core. Dello specifically requires the use of an inner exhaust core system that has a plurality of interconnected pipe segments.
U.S. Pat. No. 3,858,678 was granted Jan. 7, 1975 for a Muffler With Rotary Gas Flow to Ralph Haren. It is directed to a muffler construction that has an outer shell which is clamped to the ends of a flow tube which contains flow obstruction devices to prevent or restrict straight through gas flow.
U.S. Pat. No. 3,104,733 was granted Sep. 24, 1963 for a Sound Attenuating Gas Pipe to Edmund Ludlow. It is directed to an exhaust system which has an outer pipe with a plurality of sections or inserts mounted within the outer pipe that are coaxially aligned within the outer pipe to define a main gas flow passage therethrough. The combination is designed so that each adjacent pair of inserts act in combination with the adjacent wall of the outer pipe to define a xe2x80x9cresonating chamber of volumexe2x80x9d.
U.S. Pat. No. 5,799,395 was granted Sep. 1, 1998 and U.S. Pat. No. 5,907,134 was granted May 25, 1999 for Air Gap-Insulated Exhaust Pipe And Process For Manufacturing An Air Gap-Insulated Exhaust Pipe to Thomas Nording, et al. Both patents are directed to a double wall exhaust pipe wherein the inner pipe which is comprised of sections connected by a sliding fit which are prevented from contacting the walls of the outer pipe as the result of the thermal expansion of both pipes during operation.
FIG. 9 illustrates a prior art double wall exhaust pipe construction for motorcycles made and sold by Hooker. The internal hot gas bearing pipe 69 connects to the engine by a mounting flange 71 and routes the hot gases to its output end 73. The internal pipe 69 is mounted in a larger diameter external pipe 67 which has a cut-away section 75 that runs the length and shape of the internal pipe 69. The output end 73 of the internal pipe 69 slips into a slip joint 77 and is held in place by a plurality of hose clamps 79, 81 and 83 which are held to the inside of the external pipe 67 by loops 78, 80 and 82. Besides not being a very secure mounting, the heat transfer from the internal pipe 69 to the external pipe 67 still presents bluing problems. Various coatings on the internal pipe, such as a ceramic coating have been tried to prevent the bluing problem. The pipes come without a muffler. However, a muffler core can be accommodated at the output end 87 of the external pipe 67. The manufacturer recommends using either a louvered core or a tuned core. Inserting a louvered into the output end 87 of the external pipe 67 creates a single wall muffler with the hot exhaust gases contacting the internal surface of the external pipe 67 at the output end 87. This creates bluing of the output end 87. A tuned core is simply a pipe extension that may vary in diameter from the internal pipe 67.
Applicant""s double wall pipes and muffler have solved the heat discoloration problem which the prior art has been unable to do.
A decorative chromed exhaust pipe for internal combustion engines is provided which does not discolor from the heat generated by the exhaust gases flowing from the engine through the pipes and to and through the muffler. A double-walled muffler is completely encased by an interior casing which only allows gases to flow out the back end of the housing. The exhaust pipe, from the mounting flange to the double-walled muffler has a double wall construction with the exterior wall chromed. The exterior chromed pipe is cut-away on its back side, from the mounting flange to the muffler, allowing the interior one piece pipe to be inserted through the cut-away section and be air cooled during movement. Mounting flanges are welded to the exterior and interior pipes at the back for mounting the exhaust pipe to the vehicle and to hold the interior pipe in a spaced apart relation to the exterior pipe. For larger pipes, separate spacers are welded to the exterior and interior pipes to hold the interior pipe in a spaced relation to the exterior pipe. During operation, the cut-away back side of the exterior pipe provides cooling to the exterior pipe sufficient to prevent heat discoloration of the exterior pipe under the heaviest load conditions. The double-walled construction of the muffler with an air layer between the outside wall and the inside wall prevents the muffler from bluing. In the case of dual exhaust pipes, a Y-shaped collector routes the exhaust from both pipes into the double-walled muffler.